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In Exercises 81 - 112, solve the logarithmic equation algebraically. Approximate the result to three decimal places. \( \ln x - 7 = 0 \)

Short Answer

Expert verified
The solution to the equation \( \ln x - 7 = 0 \) is \( x = 1096.633 \) when approximated to three decimal places.

Step by step solution

01

Move -7 to the other side

Add 7 to both sides to isolate the \( \ln x \) term on one side of the equation. This results in \( \ln x = 7 \).
02

Convert the logarithm equation to an exponential equation

The equation \( \ln x = 7 \) is equivalent to the exponential equation \( x = e^7 \) since the natural logarithm uses the base 'e'.
03

Numerical approximation to three decimal places

Using a calculator, the numerical value of \( e^7 \) is approximately 1096.633, but approximating to three decimal places results in the final answer x = 1096.633.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Natural Logarithms
Natural logarithms are a special type of logarithm that use the base 'e'. The notation \( \ln \) stands for natural logarithm, and it refers to logarithms with base 'e', which is approximately 2.718. In mathematical expressions, when you see \( \ln x \), it means the natural logarithm of \( x \). These types of logarithms are very common in calculus and are essential for solving logarithmic equations. In the exercise given, the equation \( \ln x = 7 \) asks you to find the value of \( x \) such that the logarithm of \( x \) with base 'e' equals 7.
  • \( \ln x \) implies base \( e \) logarithm of \( x \)
  • The aim is to find \( x \) when \( \ln x = 7 \)
You can think of natural logarithms as the inverse operations to exponential functions, particularly those involving base \( e \). This characteristic makes them particularly useful for finding unknowns in exponential equations.
Exponential Equations
Exponential equations involve variables in the exponent, with a constant base. They often require logarithms to solve, especially when the variable is inside the exponent. After isolating the \( \ln x \) term in the equation \( \ln x = 7 \), changing it into an exponential equation is a crucial step. Here, the logarithmic equation \( \ln x = 7 \) is converted into the exponential form \( x = e^7 \).
  • Exponential form expresses as \( base^{exponent} \)
  • Here it becomes \( x = e^7 \)
In simple terms, since \( \ln x \) uses base 'e', to convert \( \ln x = 7 \) into an exponential equation, interpret it as the number \( x \) for which raising \( e \) to the 7th power gives you \( x \). Solving this helps us determine the precise value of \( x \).
Numerical Approximation
Numerical approximation is crucial when dealing with values like \( e^7 \) that result in long decimal numbers. Typically, in mathematical problems, results are rounded off to a manageable number of decimal places for ease of use and practicality. In this case, we need to approximate \( e^7 \) to three decimal places. Using a calculator to compute \( e^7 \), you obtain approximately 1096.633.
  • Initial calculation might show a value like 1096.633158...
  • For practical purposes, round to three decimal places: 1096.633
This rounding allows for a clean and understandable result in calculations, ensuring consistency and precision that’s easier to interpret in practical applications, such as engineering or the sciences.
Base e
The mathematical constant 'e' is an irrational number approximately equal to 2.718281828. It's the base of natural logarithms and is a fundamental element of calculus. Its importance comes into play often in mathematical growth processes such as population growth, radioactive decay, and finance. When you see \( e \) in calculations, particularly with logarithms or exponentials, it signifies continuous growth or decay.
  • \( e \approx 2.718 \, 281 \, 828 \)
  • Serves as the foundation for natural logarithms
  • Key to solving equations like \( \ln x = 7 \)
In the equation from the original exercise, \( \ln x = 7 \) translates to \( x = e^7 \). This demonstrates how 'e' acts as the base number being raised to power, illustrating its role in solutions involving exponential growth or value calculations. Understanding 'e' is essential for solving problems that revolve around these types of equations.

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